The entire disclosure of Japanese Patent Application No. 2000-384,405 filed on Dec. 18, 2000, including specification, claims and summary is incorporated by reference in its entirety.
1. Field of the Invention
The present invention relates to a pneumatic motor and a pneumatic hoist apparatus installed with the pneumatic motor.
2. Description of the Related Art
Hitherto, a pneumatic hoist apparatus is generally comprised of a drive portion consisting of a pneumatic motor and a decelerating mechanism, a brake portion consisting of a rotary abrasion plate, a pressure spring and a release cylinder, a control portion consisting of a valve mechanism for controlling a drive portion and a brake portion, and a winding portion consisting of a chain and a wheel.
The pneumatic motor of the pneumatic hoist apparatus may generally comprise a vane motor, an axial piston motor or a radial piston motor. Out of these pneumatic motors, the vane motor has a lower level of abrasion at a rotary seal part of a cylinder chamber and allows rotation at a higher speed, as compared with the piston motors. The piston motors have a larger level of abrasion at a piston seal part, as compared with the vane motor, so that it is less suitable for rotation at a high speed. It has the advantage, however, that the cylinder chamber can be readily rendered airtight and volume efficiency can become great. Further, it can readily make the effective pressure receipt area of the cylinder chamber greater so that the pneumatic motor itself can be easily provided with torque at a high output.
Each of the pneumatic motors, however, suffers from the following disadvantages.
The vane motor has the defect that its mechanical efficiency is low. For example, it is so difficult to raise the air tightness of its cylinder chamber. Further, it is also difficult to increase an effective pressure receipt area of the cylinder chamber. Therefore, it is required to rotate its pneumatic motor at a high speed in order to gain a high output torque and to use the pneumatic motor in combination with a deceleration mechanism having a high deceleration ratio. Moreover, it has the defects that air may be leaked and noises may be caused due to rotation at a high speed.
On the other hand, the conventional piston motors require the installation of a crank mechanism or a swash plate mechanism for converting a linear movement of a piston into a rotational movement of its motor shaft. This leads to an increase in resistance to abrasion resulting in a low mechanical efficiency.
As described above, each of the vane motor and the piston motor has its merits and demerits, although the vane motor is leading the piston motor based on its advantage of manufacturing costs.
The vane motor, however, still has the problems with from preservation of the environment, labor circumferences, etc. To saving energy and rendering noises lower. Therefore, the development of a pneumatic hoist apparatus with a pneumatic motor has been demanded, which can solve the above problems as well as increase mechanical efficiency has been demanded.
The present invention has the object to provide a pneumatic motor that can solve the disadvantages inherent in the conventional motors.
The present invention has another object to provide a pneumatic hoist apparatus installed with the pneumatic motor that can solve the disadvantages of the conventional motors.
In order to achieve the object, the present invention in one aspect provides a pneumatic motor comprising twin cylinders each with a piston installed slidably therein and disposed horizontally adjacent in a direction parallel to an axis of a motor shaft interposed between the twin cylinders and disposed in a direction intersecting with each of the twin cylinders at a right angle. An association unit connects the motor shaft to each of the pistons and is adapted to convert a liner movement of each of the pistons into a rotational movement and transmit the rotational movement to the motor shaft. The twin cylinders, the motor shafts and the association unit are installed integrally in a casing. The association system is coupled with end an portion of each of a first eccentric shaft and a second eccentric shaft, which in turn are disposed projecting from the motor shaft in opposite directions at a phase angle of 90 and coupled with a first eccentric pin and a second eccentric pin in an eccentric state, which in turn are coupled in association with the respective pistons. A pinion gear is disposed in mesh with a ring gear mounted integrally in a motor chamber on an outer periphery of the first eccentric shaft and the second eccentric shaft.
In a preferred embodiment, the present invention provides the pneumatic motor in which the first eccentric shaft and the second eccentric shaft are connected to the center of the piston shaft with a piston disposed at each of the both ends thereof.
In a more preferred embodiment, the present invention provides the pneumatic motor in which the diameter of a pitch circle of the pinion gear disposed on each of the first eccentric shaft and the second eccentric shaft is set to twice the amount of eccentricity from the motor shaft of each of the first eccentric shaft and the second eccentric shaft and the diameter of a pitch circle of the pinion gear disposed on each of the first eccentric shaft and the second eccentric shaft is set to double the amount of eccentricity of the first and second eccentric shafts, while the axial center of the eccentric pin disposed on each of the eccentric shafts is located on a periphery of the pitch circle of the pinion gear.
In a more preferred embodiment, the present invention provides the pneumatic motor in which, as the axial center of one of the first and second eccentric pins reaches a periphery of the pitch circle of the ring gear, the axial center of the other eccentric pin is arranged so as to simultaneously reach the central position of the pitch circle of the ring gear.
The present invention in another aspect provides a pneumatic hoist apparatus installed with the pneumatic motor in each of the embodiments as described above, in which a motor control chamber is disposed under the cylinders, the motor shafts and the association system are disposed in the casing of the pneumatic motor, and a valve mechanism system is disposed in the motor control chamber and is so adapted as to rotate the pneumatic motor in normal and opposite directions by controlling the supply of air to the pneumatic motor and the discharge of air therefrom. A chain sprocket is coupled with the motor shaft with the aid of a gear and is disposed in a direction parallel to the axis of the motor shaft and with a chain wound thereon, the chain being mounted on the chain sprocket with a hook for hoisting goods or the like at its bottom end.
In a preferred embodiment of the another aspect, the present invention provides the pneumatic hoist apparatus having a remote control portion disposed nearby above the hook for hoisting goods or the like, from which the operations for rotating the pneumatic motor in normal and reverse directions and for terminating the rotation of the pneumatic motor can be controlled